The invention relates to methods and systems for the diagnosis and management of attentional disorders.
Alterations in locomotor-activity levels and disturbances in rest-activity rhythms have long been recognized as an integral sign of many psychiatric disorders. For example, the hyperactivity of children with Attention-Deficit/Hyperactivity Disorder (ADHD) is most readily discernible as a failure to inhibit motor activity to low-levels.
Using precisely quantified movements, ADHD children have been shown to move their head 2.3 times more often than normal children, moved 3.4 times as far, cover a 3.8-fold greater area, and have a more linear and less complex movement pattern. Teicher et al., J. Am. Acad. Child Adolesc. Psychiatry 35:334 (1996). ADHD children also have disturbances in their ability to perform on cognitive control tasks. These disturbances can be reflected in conventional measures of performance such as accuracy, omission and commission errors and response latency, along with measures of fluctuation in attention states. Teicher et al., J. Child Adolesc. Psychiatry 14:219 (2004).
The problem is that dozens of measures have been described that quantify aspects of attention and activity. From this array of potential measures it is unclear which measures should be used for clinical purposes. There is a need for reliable, inexpensive, and easy to use methods to derive a small number of omnibus composite measures that are most suitable for diagnosing attentional disorders and for assessing how subjects change over time and with therapy.
Previous attempts have been made to provide a reduced number of composite scores. The Conners' CPT-II test provides a single composite called the Confidence Index that suggests closeness of the match to a clinical or non-clinical profile. This composite index uses only attention variables, and has been reported in independent samples to fail to distinguish between children with and without ADHD (Edwards et al., J. Abnorm. Child Psychol. 35:393 (2007)). Similarly, it has been reported to fail to distinguish between adults with and without ADHD (Solanto et al., CNS Spectr. 9:649 (2004)).
The McLean Motion and Attention Test (M-MAT) used principal component analysis (PCA) to reduce the number of activity and attention measures. From all 6 activity measures two composites were derived (“hyperactivity”, “movement area”), and 4 composites were derived from all 6 attention measures (“inattention”, “impulsivity”, “latency”, “variability”). While this approach reduced the number of measures, it did not do so to a sufficient degree. Further, applying PCA separately to a moderate number of activity and attention performance measures does not yield composites that are optimal as treatment-responsive measures of attention disturbance and motor activity disturbance. This is because the distribution of scores for the populations normal and abnormal subjects obtained using these M-MAT composites do not provide enough differential between typical ADHD subjects and typical non-ADHD subjects and too much of the dynamic range of the M-MAT composite curve is dictated by extreme scores, rather than the range between normal and abnormal (e.g., the range in which partially treated subjects would be found). As a result, the M-MAT composite score is insensitive to change in a subject (i.e., such as a modest improvement resulting from therapy, or a change in the subject over time). Moreover, the M-MAT composites are not bounded between set limits and are not scaled in a way that is readily interpretable clinically.